The invention is concerned with improvements in or relating to the mounting of tool blades in tools. More particularly, but not exclusively, the invention finds use in the mounting of one or more contoured blades in a tool body for use in a tool holder of a rotary machine tool for example for boring or milling. Such blades may be made for example from tungsten carbide, high-speed steel or from ceramic material.
It has been common practice to mount such blades in a tool body either in a permanent or replaceable manner. In the former case, the blades may be secured in a seating channel by brazing or bonding but considerable stresses are produced caused by differences in the co-efficients of expansion of different metals. Stresses built up in a tool body and in the blade through repeated heating and cooling caused for example by the brazing process frequently cause fractures which necessarily result in rejection as unsuitable for subsequent use.
In the latter case, blades may be secured in the seating channel by clamping pressure exerted by screw wedge devices. If the pressure is too great, the blades may fracture in use or, if not firm enough the blades may come loose and be ejected from the tool body by centrifugal force. This possibility presents considerable risk of product damage or injury to factory personnel, since tool operating speeds may be between for example 6,000 r.p.m. and up to 30,000 r.p.m. or more.